Losing weight rapidly

[Charley Chuckles]

My fat boy who is 12 and a half years young has in the past few weeks not wanting to eat much, he's even gone off blocks 🥺
I've bought baby food squash and such he eats a small amount. I was cooking squash slightly to make it soft he had incisors removed from odatoma years ago he only has slight bottom incisors.
Long story longer I guess, he's just not wanting much I even make him FV he'll have a little, now if I give him a piece of Pizza crust it's gone in a flash🥴
Any ideas what might help him eat better 🤷
Mind you he's a FL grey and weighs 695g of this morning, he's dropped from 720g recently.
I know he's still a big boy and I did want him to drop some weight just not so fast and not by not wanting to eat☹️